Don’t hold your breath waiting for the most politicized Justice Department in American history to drop its imperious lawsuit against the people of Arizona — those impertinent subjects who dare to demand enforcement of the immigration laws Pres. Barack Obama deems null and void.

It is true that this week, in upholding Arizona’s sanctions against employers who hire illegal aliens, the Supreme Court implicitly undermined the preemption-by-executive-fiat theory underlying the administration’s suit. By a 5–3 majority (with Justice Elena Kagan, Obama’s former solicitor general, having recused herself), the Court held that a state is not barred from enacting laws that are consistent with federal statutes and bolster congressional purposes. That is to say, the touchstone of preemption remains law, which is what Congress prescribes, not policy, which is a president’s political calculation about what laws to enforce or not enforce.

That ought to spell doom for DOJ’s civil-rights case against Arizonans, who are doubly afflicted by a federal government that taxes them to support agencies that first refuse to protect them and then haul them into court for trying to protect themselves. The state’s controversial immigration-enforcement law (known as “Senate Bill 1070”) actually strengthens federal laws that bar aliens from entering and remaining in the United States illegally. Given the justices’ apparent enthusiasm for state statutes that support and bolster federal statutes, one might think Attorney General Eric Holder would read the writing on the wall and call off his minions.

He won’t. Obama’s tyrannical preemption theory is damaged by Thursday’s ruling in Chamber of Commerce v. Whiting, but it is not destroyed. Nor is that the lone cause for disappointment — far from it. While the Court’s bloc of progressive activists lost this skirmish, they’re winning the federalism war in a rout. Whiting leaves in tatters the concept of state sovereignty, federalism’s bedrock.

For that, Arizona can place much of the blame on itself. Chief Justice John Roberts’s majority decision boldly asserts that the “power to regulate immigration is unquestionably a federal power.” Arizona has mounted no meaningful resistance to this proposition, neither in Whiting nor in the ongoing litigation over the more hotly disputed Senate Bill 1070. Thus, it is perhaps to be expected that this is the one point on which all nine of the Court’s justices seem to be in agreement.

Chief Justice Roberts’s assertion is untrue, at least insofar as it implies federal supremacy over the question of immigration. As I’ve previously contended, there is nothing in the Constitution that vests the federal government with the power to police illegal immigration within the territory of a state. To the contrary, the Constitution empowers Congress merely “to establish an uniform Rule of Naturalization,” i.e., to prescribe the qualifications for American citizenship. It says nothing about how those standards are to be enforced. In adopting the Constitution, the states did not delegate to the national government their inherent authority to police their territory, to defend their citizens, and to detain persons who have no lawful right to be on their soil.

In the debates over the adoption of the Constitution, such leading proponents as Hamilton and Madison assured the wary states that they would retain control over the administration of justice within their territories. The federal government’s concerns would be limited to such “external objects” as “foreign commerce.” The states would continue to focus on those “internal objects” that “concern the lives, liberties, and property of the people,” including the “internal order of the state.”

Thus the question was not whether the states were “preempted” from regulating or prohibiting the activities of non-citizens within their territory. It was whether the national government had any power over immigration enforcement. The “unquestionable” power was state power. That is why, in its 1837 New York v. Miln decision, the Supreme Court upheld a state law that allowed New York City to expel arriving aliens it deemed likely to become a public burden. As Justice Philip Barbour explained, the state had acted

to prevent her citizens from being oppressed by the support of multitudes of poor persons who come from foreign countries without possessing the means of supporting themselves. There can be no mode in which the power to regulate internal police could be more appropriately exercised. New York, from her particular situation, is perhaps more than any other city in the Union exposed to the evil of thousands of foreign emigrants arriving there, and the consequent danger of her citizens being subjected to a heavy charge in the maintenance of those who are poor. It is the duty of the state to protect its citizens from this evil; they have endeavored to do so by passing, amongst other things, the section of the law in question. We should, upon principle, say that it had a right to do so.

The oppression then faced by New Yorkers pales in comparison to what is happening in modern Arizona, where — in addition to heavy charges for the subsistence, education, and medical needs of an exploding illegal alien population — citizens are besieged by the militias and drug gangs of a disintegrating Mexico. Yet, from its original posture of great difficulty identifying a source of federal authority over immigration enforcement, the Supreme Court suddenly decided, with the dawn of the Progressive era, that the national government had somehow become preeminent in the field.

That is the tack taken by Chief Justice Roberts, joined in the Whiting majority by Justices Scalia, Kennedy, Alito, and, with some apparent but unexplained reservations, by Justice Thomas (who concurred in the judgment but joined in only parts of Roberts’s opinion). Arizona’s law enabling the state government to revoke the licenses of businesses that knowingly hire illegals was upheld, but only because Congress had expressly permitted the states to enact such regulations. Arizona’s requirement that all state employers use the federal E-Verify system to ensure that applicants are entitled to work was likewise upheld, but only because Congress had not barred the states from imposing such a requirement, and because the executive branch (during the Bush administration) had characterized Arizona’s E-Verify mandate as “permissible.”

Plainly, the Court’s unanimous position is that the federal government, in its unfettered discretion, may prevent the states from conducting any immigration enforcement, no matter how threatened the states may be by illegal immigration and no matter how resolutely the president refuses to address such threats. The justices divide only over whether the federal government has already prohibited state action; the dissenters (Justices Breyer, Ginsburg, and Sotomayor) contend that it has, implicitly if not explicitly. There is no reason to think Justice Kagan would not have voted with them.

This leaves the states at the mercy of Big Brother for their internal defense, and that is a huge problem. The right of self-defense is a core aspect of sovereignty. If the states no longer have it, they are no longer sovereign, meaning the foundational assumption of our constitutional system no longer obtains.

On the right, commentators are gliding past this looming catastrophe and focusing on the good done by the ruling. To be sure, the validation of a state’s ability to shut down the employment magnet is essential if illegal immigration is to be reduced from a crisis to a nuisance. But this judicial validation is based on the whim of Congress rather than the inherent power of sovereign states. That is not very reassuring: If the years 2007 through 2010 taught us anything, it is that a Congress in the grip of ideology can and will govern against the will of the majority.

And it may not just be a Congress in the grip of ideology that we need concern ourselves about. Yes, much of the Whiting majority opinion appears to dismantle the Obama administration’s theory that state power can be preempted by presidential diktat. Chief Justice Roberts repeatedly emphasizes that Arizona’s alien-employment statute “trace[s]” the analogous federal statutes.” He reasons that the question of whether states are preempted from regulating is controlled by the language Congress enacts into federal law. And he pointedly rejects the argument frequently urged by centralizers that immigration must have a one-size-fits-all enforcement scheme imposed by Washington. “The prospect of some departure from homogeneity,” Roberts explains, is a feature of “our federal system.”

Were the federal courts to hew to this Supreme Court guidance, the Obama administration would have to lose its lawsuit against Arizona. Furthermore, as an ethical matter, the Justice Department should abandon any case in which the law dictates that it should lose, even a case that excites the political base the president badly needs to excite if he is to win reelection. A Justice Department that abandoned a sure winner like the Black Panthers voter-intimidation case should, after Whiting, drop its Arizona case forthwith.

Don’t hold your breath. Obama’s loyalists and the open-borders crowd will observe that Whiting did not present a preemption claim rooted in presidential policy rather than statutory law. That this actually makes Obama’s case against Arizona’s Senate Bill 1070 weaker won’t matter; it is a distinction Holder’s Justice Department can point to as a reason for pressing ahead.

Moreover, in one brief section of the Whiting opinion, the chief justice takes pains to distinguish Arizona’s alien-employment law from state laws the Court has occasionally invalidated because they contravened presidential policy in the field of foreign affairs. For a non-political Justice Department in an era more faithful to the federalist underpinnings of our Constitution, those cases would not save the Arizona lawsuit. After all, the conduct of foreign relations is a core power of the presidency — states should not interfere with it, because it is the principal “external object” the federal government was created to manage.

By contrast, immigration enforcement is a traditional responsibility of the states, an “internal object” and an incident of sovereignty. Or at least it used to be.